Abstract
Introduction. Today, the number of publications on concrete with an admixture of graphene and graphene oxide has exceeded 3000. However, there is a drawback to these works (in large quantities), which is that when producing concrete, there is no control over the number of graphene monolayers, and for natural graphite the number of monolayers is three. When the number of monolayers exceeds three, it turns into graphite, the properties of which are different from the unique monatomic graphene. Therefore, there is a large difference in the properties of concrete in published works. Aim. To develop a technology for producing graphene concrete with a controlled number of graphene monolayers and to investigate the effect of graphene and graphene oxide on concrete wear resistance. Materials and methods. Standard concrete was prepared as follows: an aqueous solution with graphene oxide (GO) and reduced graphene oxide (rGO) was placed in a bath, where an ultrasonic emitter created an ultrasonic field and the graphite and graphite oxide were separated into monolayers of graphene and graphene oxide; the frequency of the ultrasonic field was selected from the “latent” energy of deformation of the samples; graphite delamination was monitored using UV and Raman spectra; M400 cement; crushed stone with grain sizes of 5–20 mm; sand grade M2.5–2.9; VORONEZHFortis mixer; vibrating table; concrete volume 10 L. The resulting concrete samples were tested on a PGM-2000MG4 press. Results. In the period from 1 to 7 days, the compressive strength of the samples relative to the control samples increased from 13 to 63 %, and up to 14 days from 16 to 62 %. Regarding the effect of the graphene suspension, the following conclusion can be made: stratification of graphite and graphite oxide into monolayers of graphene and graphene oxide occurs in an ultrasonic field of a certain frequency; the large specific surface area of graphene and graphene oxide serve as a source of crystallization and hardening of concrete. The above effects are especially pronounced at concentrations of graphene or graphene oxide in the range of 0.05 0.07 % of the concrete mixture. At higher concentrations, coagulation of graphene monolayers and their transformation into graphite occurs. To obtain highly wear-resistant graphene concretes in production, it is necessary to adhere to the regulations for obtaining a suspension in an ultrasonic field, as described above. Conclusions. The article proposes a model of cracks in graphene concrete based on the theory of catastrophes, from which it follows that both graphene and graphene oxide enter the interlayer region, destroying the structure of the C–S–H gel due to a sharp decrease in the molar mass of the compound. This is a brake on the movement of nanocracks that occur in any solid when its surface is formed. It has been shown that modifing concrete with graphene oxides increases its wear recistence by 4-5 times compared to standard concrete.